Carburetor



s. CQ SMITH CARBURETOR Oct. 24, 1944.

Filed Sept. 23, 1937 4 Sheets-Sheet l INVENTOR. STuYw-:saur C, SMITHTToRNEY.

S. C. SMH-H CARBURETOR l Oct. `24, 1944.

Filed Sept. 25, 1937 4 Sheets-Sheet 2 INVENTOR,

S. C. SMITH CARBURETOR Oct. 24, 1944.

Filed Sept. 25, 1937 I 4 SheetS---Sheel'l 3 S. C. SMITH CARBURETOR Oct.24, 1944.

Filed Sept. 23, 1957 4 Sheets-Sheet 4 R. Hl m m5 1Q T .N H V w T .5

Patented Oct. 24, 1944 CARBURETOR Stuyvesant C. Smith, South Bend, Ind.,assignor 'to Bendix Aviation Corporation, South Bend, Ind., Iacorporation of Delaware ApplicatonSeptember 23, 19377, Serial No.165,248 Y 1oA claims. (ci. 12s-119) This invention relates .tocarburetors and ,more particularly to mechanism adapted forautomaticallycontrolling the'carburetor choke.

The present application is a continuation in part of my copendingapplications `Serial No. 641,898, filed November '9, 1932, and SerialNo. 41,439, filed September 20, `1935 (divisionof application Serial No.653,500,1iled January 25, 1933,

now issuedas Smith-Patent 2,030,331).

Carburetors for internal combustion engines,l in -order to be automaticin operation, must vbe adapted under all conditions to vsupply a fuelmixture proper for the particular stage of operation of the-engine.During engine starting, `when the engine is cold and cranked at a speed=gen erally lower than its normal idling speeds, provision must -be madefor an excessively rich mixture, and immediately the lengine commencesto iire, and the speed is correspondingly increased, together withlengine suction, the mixture ratio#- must be reduced, and thereaftercontrolled according to requirements and regulated accordingly.`'Ii'hese varying conditions require `tremendous and rapid changes inthe various carburetor control elements to meet the requirementsvexisting at various stages of engine operation. This invention isdirected Vtoward automatically controlling particularly fthe choke valveand throttle valves during engine starting and running by theutilization of the many variables in engine operation such astemperature, Ymanifold suction, intake suction, speed, etc. in' variousnovel and related fashions Ito produce substantially correct mixturesfor the `various engine operating conditions. p

Certain embodiments of the present invention include a thermostat whichis connected to the choke valve of the carburetor to control the.richness of the 4mixture produced thereby, and a vacuumactuated .piston.coupled to the valve and thermostat by a spring which .is tensionedtooppose `the tension of the thermostat, this spring being adjustable sothat .the setting of the valve can be accurately controlled.

. .4 An object ofthe invention Ais to provide m a 5 carburetor anautomatic choke adapted to .close- `ly follow and respond-'to thevariations in engine requirements by :utilization yof engine temperatureand speed or dependent variables thereof.

A further object is to provide an automatic choke havingthermo-sensitive means with mechanism whereby the effect ofthe'thermo-sensitive means maybe varied upon engine starting.

Another object is to provide in a carburetork fa novel `mechanism forpositively cracking the throttleduring choking.

A still further object yis to .provide an automatic 'choke adapted to.operate a plain balanced choke valve.

Still another `object of the .invention is to pro- ...vide a choke valveof simplified lconstruction and 1- having a minimum of parts.

A still further object is `to provide a thermostatically controlledchoke valve, wherein manifold vacuum is adapted to vary the eliect ofthe i thermostat.

Still lanother object is to provide a `mechanism controllable by thecarburetor Ythrottle valve, whereby the choke can be positively openedfor airing out after .iiooding Yet a further object is the provision ofa thermostatic control adapted to urge a choke valve open or closeddependent on temperature, and vacuum loper-ated Ymechanism for openingthe choke slightly upon engine starting, and prior t warming up.

A further object is the provision of manifold' vacuum sensitivemeans forvarying thermostatic vchoke action.

rl'he above yand :other novel features of the invention will appear more`fully hereinafter from the following detailed-description when taken inconnection with the accompanying drawings. It is expressly understood,however, that the `drawings yare employed for purposes of illustrationonly and are not designed as a definition of the limits of theinvention, freference lbeing had for this purposeto the appended claims.

In the drawings wherein like reference numerals indicate like parts;

Figure 1 is a diagrammatic view, partly in section, showing theapparatus of the invention;

Figure 2 is a view similar to Figure 1 showing another modification;

Figure 3 shows the invention adapted to a particular carburetor;

Figure A is a view similar to Figure 1 showing Vanother modication ofthe invention;

Figure 5 .isa View of the control mechanism of the inventionapplied t'oa carburetor that is located at a point remote from the exhaustmanifold;

Figure 6 vis a crosssectional View taken along the line 6--6 of Figure5.1ooking in the direction of the arrows.

. Figure 'lis a View in elevation partly in section,

fof another form of the invention;

Figure 8 is a view-in elevation partly in section,

of a carburetor embodying a further modified form of the invention;

Figure 9 is an elevation partly in section, of a further modified formof the invention;

Figure 10 is a view in elevation partly section, of a further modifiedform of the invention; and

Figure 11 is a sectional view of one form of thermostatic elementadaptable for use in the modified form of Figure 7.

Referring now to the drawings in more detail, the apparatus shown inFigure 1 includes a car-V buretor I having a balanced choke valve I2 anda throttle I4. The carburetor is shown as a plain tube down draftcarburetor, this type being illustrated by way of example only as theinvention may be applied to other types of carburetors within theteachings of the invention. The shaft I3 of the choke valve carries alever I5 fixed thereto and a lever I8 is fixed on the shaft of thethrottle. These levers are connected by a rod 20 connected to lever I5and coupled to lever I8 by a lost motion connection. As thethrottleapproaches its wide open position, lever I8 operates rod 26 tocrack the choke valve so that ailooded condition of the engine can becorrected. The amount that the choke valve is opened is governed by anadjusting nut 2|. The choke valve I2 is provided with a small poppetvalve I6 of known construction to admit air for starting.

A thermostat casing 22 is mounted upon a suitable bracket 23 xed uponthe intake manifold of the engine adjacent t0 the carburetor. and ashaft 26 is journaled in the casing. Athermoresponsive element 28 isfixed to the shaft and wound therearound and is disposed so as to beheated by heat radiated from the exhaustmanifold of the engine. The freeend of the element bears against astud 36 projecting from the casing. Anarm 32 is fixed upon the shaft and its free end is connected to thechoke lever I by a rod 34. When the engine is cold thermostat 28 istensioned to rotate lever 32 and close the lchoke valve and to maintainit closed during starting.

A cylinder 36 is mounted upon the intake manifold 24 and communicatestherewith through a 'suitable port 31. A piston 38 is fitted in thecylinder and urged upwardly therein by a spring 40. A rod 4I is iixed tothe piston and extends through an ear 42 on lever 32 and therebeyond,

the end of the rod being threaded to receive an adjusting nut 44. Asleeve 45 formed on nut 44 surrounds the rod, and va spring 46 surroundsthe sleeve and bears against ear 42 and nut 44.

When it is desired to start the engine the throttle is set to startingposition, that is, about one fourth open, and the choke valve is closedby the automatic mechanism just described. The engine is cranked and assoon as it begins firing piston 38 is drawn downwardly against thetension of spring 46. Sleeve 45 engages ear 42 and moves lever 32 tocrack the choke valve so that the engine will not stall. Spring 46 istensioned in opposition to the tension of the thermostat. As the enginewarms up, the thermostat tension decreases and spring 46 moves lever 32to open the choke valve more and thereby reduce the richness of the.fuel mixture. As the choke valve opens the tension of spring 46decreases as lever 32 moves away from nut 44. When the normal operatingtemperature of the engine is reached, ther-y mostat 28 will have zerotension and the choke valve will be fully opened. As the thermostat isheated further, as it will be by heat radiated from the exhaust manifoldof the engine, the end of the ele-ment moves away from bracket 30 andengages a second bracket 48. The thermostat is then tensioned in theopposite direction to aid spring 46 in holding the choke valve open. Theparticular type of thermostat shown is not new, being shown and morefully described in the copending application of S. F. Hunt, Serial No.647,641, filed December 16, 1932. When the engine is stopped, spring 40raises the piston and the tension of spring 46 is reduced. As the enginecools down, the thermostat is retensioned and le- `ver 32 operatedthereby to close the choke valve.

In the modification shown in Figure 2 thermostat shaft 26 carries amultiarm lever 66 and choke valve control rod 34 is connected to thefree end of one of the arms. A pivoted lever 68 is connected to piston38 and provided with an ear 42 through which a rod 10 extends. The rod10 is connected to one of the arms of lever 66. A sleeve surrounds therod, and a spring 46 surrounds the sleeve and bears against the ear anda nut 44 as before. A third arm of lever 66 carries a pin 1I againstwhich a lever 12 is adapted to bear. Lever 12 is connected iby rod 13 tothe throttle lever and the lever 12 thus moves the pin and lever 66 tocrack the choke valve when the throttle is Wide open.

In the operation of the device, the thermostat is tensioned to hold thechoke valve closed when the engine is cold. When the engine fires,piston 38 is drawn into the cylinder and spring 46 tensioned to opposethe tension of the thermostat to permit the choke valve I2 to open underthe pressure difference on its faces. The tension of spring 46 isadjusted by nut 44 as before.

In Figure 3 I have shown the invention adapted to a carburetor having achoke valve which comprises two leaves 14 which are hinged to the sidewalls of the structure. A stud 15 is fixed in the carburetor midwaybetween the leaves of the Valve. A collar 16 is mounted on the stud forsliding, and is urged upwardly thereon by a spring 11. Collar 16 isgrooved to receive the ends of arms 18 which are fixed on the leavesadjacent to the hinges. Air pressure on the upper face of the leaves andvacuum on the lower faces causes the leaves to swing on their hinges andthe collar to move downwardly against the tension of spring 11. In thecontrol mechanism, thermostat arm is fixed on the thermostat shaft andconnected by a rod 8| to a pivoted lever 82 which carries an ear 42.Piston 38 is urged upwardly in cylinder 36 by spring 40 and carries rod4I which extends through the ear and is threaded to receive nut 44 bywhich spring 46 and sleeve 45 are held on the rod. A bell crank lever 84is pivoted adjacent to lever-82 and carries an ear 85 through which rod86 slidably projects. One end of this rod is pivotally connected tolever 82 and the other end is threaded to receive a nut 81. A spring 88surrounds the rod and bears against ear 85 and nut 81. A crank arm 90 isjournaled in the carburetor casing and connected to lever 84 by a rod9|. The free end of arm 90 bears against one of the leaves of the chokevalve.

When the engine is cold and not running, thermostat 28, which is of thetype shown in copending application of S. F, Hunt, Serial No. 647,641,above referred to, is tensioned to raise arm 80 and thereby rotate lever82 clockwise on its pivot. Spring 88 is tensioned to rotate arm 84 andwith it arm 96 to close the choke valve. The thermostat is tensionedsufliciently to keep the valve closed during starting of the engine.When the engine fires, piston 38 is drawn downwardly in the cylinderagainst the tension of spring 4U and spring 46 is -ten'sioned to opposethe thermostat 'and rsleeve =45 engages and moves lever 82counterclockwise. The tension :of spring 88 is relieved .and the chokevalve opened slightly. ySince the tension of spring :opposes thethermostat tension the effective force holding the valve closed isinsufficient to resist the air pressure on it. The thermostat isarranged to decrease its'tension as the engine warms up and the valveopens wider, being fully opened when the enginereaches normal operatingtemperature. As. the valve opens, tension is built up in spring 1.5.When the engine is `stopped spring '48 raises piston 38 to `decrease thetension in spring v46 and as the` engine cools tension Vis built up inthe thermostat 'and func tions to rotate farm 98 to fclose the valvewith the aid of spring 15. Adjustments of the vchoke setting are made byadjusting nuts A44 `and 81.

In the embodiment of the invention shown in Figure 4, the shaft ofthermostat 28 `carries a cam `82 upon which is mounted a pin 9'3. Alever 52 is pivotally mounted adjacent to the cam and connected to thethrottle of the carburetor by suitable means 53. When the throttle ismoved to wide open position, lever 52 lengages and moves cam 92 topartially open, the choke valve. VA 'shaft .94 is journaled in thecasingof the'mechah nism and carries a lever 96which is fixed thereto andcarries a roller 85 that engages the cam. A second lever 88 is fixedupon shaft 94 and connected by rod 34 to the choke valve I2. A lever 31floats upon shaft 94 and is connected to piston 38. Spring 48 urgespiston38 upwardly tomove lever 91 counterclockwise on shaft 94. Lever`86 carries an ear 89 which overhangs lever 91 so that the tensionof'spring 48 is applied to lever 88 to hold the choke valve closed. i

When the engine is cold, shaft -25 is urged `counterclockwise by thetension in the thermo; stat. A shoulder I8I on the cam strikes roller 95to apply the thermostat tension to lever 98 to aid in keeping the chokevalve closed while the engine is being cranked. Immediately the en ginefires piston 38 is drawn downwardly against spring 48 and lever 91 ismoved away from ear 99 so that the tension of spring 48 is removed fromthe valve and it is partially opened against the tension of thethermostat by the diierenoe of air pressure on its faces. As thethermostat is heated cam 92 isi-rotated clockwise. RollerA 95 rides overcam surface |88 to move lever 96 counterclockwise and thereby open thechoke valve. When the engine reaches normal .operating temperature,vroller 95 engages a concentric portion of the earn to lock the chokevalve open, and further rotation of the cam is without effect. Movementof lever 96 reengages ear 99 with Alever 91 to lock the piston in itsoperated position so that it will not be vibratedby variations inpressure in the intake manifold during operation. This feature s morefully explained in S. F. Hunt Patent 2,015,752, granted October 1, 1935.When the engine is shut down, spring 48 raises piston 38 and closes thechoke valve as soon as the tension in thermostat 28 rotates cam 82 backso that roller 95 engages surface IDD.

In many V-type engines the intake manifolds and carburetor are locatedon Ytop of the engine' and the exhaust manifolds are outside and underthe cylinders. In an arrangement of this kind the thermostat of thecontrol mechanism cannot be located sufficiently close to the exhaustmanifold to permitit to be operated by heat radiated therefrom. InFigures 5 and 6 I have shown a modification of the invention adapting itto an which air escapes engine of 'this type. In this arrangement acasing |582 is mounted upon the boss |83 on the air horn of thecarburetor `in which choke valve 'shaft .I3 .isjournaled A cylinder |84projects from the bottom of this casing 'and Vis connected by a pipe |85to the intake manifold `Iila of the engine. .A stove |86 is placed overthe exhaust manifold IIlSa of the engine and Iconnected to the casingvby .a pipe |81 so that hot air will be 'conducted to the casing- YShaft I3 projects through the casing, and thermostat element 28 is fixedto and wound around the shaft. A piston 38 iits in the cylinder andcarries -a rod H8 having a bent end over which the free end of thethermostatis hooked. A lever |08 oats on shaft I3 and the bent end ofrod lI I8 extends through and is guided by the lever. A spring y48 fitsin cylinder |84 and urges piston 38 upwardly to tension the thermostatso as to hold the choke valve closed when the engine is cold. A valveI-I2 oats upon shaft I3 and is connected to thermostat element 28 by asuitable clamp yI I3.

When the engine is not running and is cold, piston 38 is at the top ofthe cylinder and the thermostat is tensioned to hold the choke valveclosed. Immediately the` engine res, piston 38 is drawn into thecylinder against the tension of spring 48 andthe effective tensionholding the valve closed is reduced to permit the valve to partiallyopen. As the engine warms up, heat from the exhaust manifold heats stove|86 and hot air passes through pipe I 81 into casing |82 to heat thethermostat. The casing is closed by a cover |I4 which has a centralopening into which the end of shaft I3 projects and through yfrom thecasing. Thermostat it is heated and with this loss of tension, valve I2is permitted to open more nearly wide open. Preferably the thermostatwill be adjusted so that the valve will be wide open when the enginereaches its normal operating temperature. Further heating of thethermostat raises the hooked end of the element off of rod I I8 and theelement can move without damage to itself or to the casing. Thismovement of the element carries valve I I2l across the opening of pipe I81 into the casing to block oit the heat therefrom. When the engine isstopped spring 48 raises piston 38. As the thermostat cools, its hookedend is reengaged with rod I I 8 and the element is tensioned to closethe valve. Valve I I2 is moved to unblock pipe |81 and the apparatus isin readiness for another operation.

In vFigures l to 4 inclusive I have shown the control mechanism as aseparatev unit mounted adjacent to the carburetor to simplify thefigures, but it should be understood that` the control mechanism may beincluded as an integral part of the carburetor within the teachings ofthe invention. Throughout the figures parts which are not materiallydifferent in construction and function bear the same reference numerals.

In the embodiment illustrated in Figure 7 a carburetor `2I8, secured toan intake manifold 2| 2 has provided therein a Achoke valve 2| 4 andthrottle 2I6. The choke valve may be of the unbalanced buttery typehaving a valve disc 2I8 28 loses tension as mounted upon an offset shaft228, the valve disc proper being preferably provided with an inwardlyopening relief valve 222 of the poppet type as shown which is springpressed to cover relief apertures provided thereunder in the valve disc2I8. suitably secured on the end of the valve shaft 228 is a crank 228which is connected to a` rod 238 having sliding engagement with a tube232 pivotally secured to the carburetor as at 234. Fitted between thefree end of the tubel 232 and the end of the rod which projects beyondthe free end of the tube is a series or pile of thermostatic elements234' which may be inthe form of pairs of oppositely arranged bimetallicdiscs which tend to dish upon. heating, thereby tending to expand. Whenvapor filled sylphon discs 233, (see Figure 1i), are used, there isprovided a tubular sylphon core 235 to permit the passage of the rod 238therethrough. l

Preferably the rod 238 and tube 232 are so positioned as to bring thethermostatic element when cold close to a point on the motor which isquickly heated upon engine starting, which is preferably the exhaustmanifold or an exhaust heated portion of the intake manifold. Upon beingheated the thermostatic element not only opens the choke valve .butmoves to a position (shown in dotted lines in Figure '1) further fromthe source of heat and thereafter regulates the choke in a modifiedmanner. Such an arrangement provides for relatively high initial chokingand gradual lessening thereof upon engine starting.

Although when cold, the thermostat resiliently Urges the choke closed,the unbalanced valve may open slightly against the resilient urge of thethermostat in response to engine suction created when starting and priorto any heat exchange between the manifolds and the thermostat.

For proper starting it is necessary that the mixture passage of thecarburetor be opened partially so that substantial fuel charges may bedrawn into the engine and for this purpose a bypass 248 around thethrottle valve is provided. A spool valve 242 having a connection 246with the choke by means of the arm244 of the choke crank 228 is adaptedto actuate the spool valve, thereby opening the bypass during choking.The contour of the spool valve may be such as to provide a graduallydecreasing area of cross section for the channel as the choke moves toopen position or may be otherwise constructed as to provide a differentcharacteristic as may be desired.

The modified form shown in Figure 8 comprises the usual carburetor 258having a choke valve 256 and a throttle 254. To automatically regulatethe choke valve, the same comprises an unbalanced valve disc 256 mountedon a shaft 258 which is thermostatically controlled by the spiralbimetallic thermostatic element 268. To give the desired choking effectduring cranking the valve 256 necessarily must be substantially lockedclosed and for this purpose the thermostatic element is madesufficiently stiff and placed under the required tension.

Since the tension required to produce the desired choking effect at coldmotor cranking speeds is greater than that required once the enginecommences to operate, a vacuum responsive motor 262, connected either tothe carburetor mixture passage on the engine side of the throttle valveas at-264 or to the intake manifold, is provided together with aconnection 266, through resilient means to a lever arm 268 mounted uponthe choke shaft 258. As illustrated the resilient means may consist of aspring 218 threaded upon the rod 266 so as to bear upon a swivel collar212 secured to the lever 268 and upon an adjustable nut 214 upon the endof the rod. Upon high manifold vacuum, the piston 216 will be drawndownwardly within the suction motor 262 resiliently tending to open thechoke valve 256. By properly balancing the resiliency andtension of thespring 218 and the thermostatic coil 268, an operating combinationresults which is capable of supplying the proper mixture to the engineunder substantially all circumstances, and by further proper selectionof the spring characteristics and by proper adjustment, the control maybe applied to a choke utilizing a common balanced butterfly valve, ofthe same lgeneral type as the throttle valve 254.

Since it often occurs that an engine is cranked with the ignitioncircuit open by mistake, or for some reason or other the engine becomesflooded, there may be provided a connection between the choke valve andthrottle so that the choke valve can be positively opened to air themotor out and discharge excess fuel into the vexhaust passages. For thispurpose there is illustrated a connecting link 288 pivotally connectedbetween the lever 268 on the choke valve and the crank 284 on thethrottle valve 254. So that ordinarily the operation of the throttle maynot disturb the automatic operation of the choke valve, the link 288 ispreferably connected to the throttle by a lost motion connection asshown wherein the rod or link 288 slidably engages a swivel collar 285secured to the crank 284, and provided at its end with a collar 286,which is adapted to engage the swivel collar upon opening the throttlewide, so that further movement may open the choke.

Referring to the modification of Figure 9, there is shown a downdraftcarburetor 298 having an unbalanced choke valve 292 and throttle 294.Secured to the choke valve shaft 286 is a double crank member 298,operatively connected through a link 38| to a crank 382 actuated by athermostat 384. A lever 386, pivoted on the choke shaft 296 is adaptedto operate between spaced pins 388 on the crank member 298, therebyproviding a lost motion connection. A vacuum operated cylinder 38Thaving a piston 388 is connected to the intake manifold preferably atany point on the engine side of the throttle valve 294, and is adaptedthrough the piston 388 and link 3|8 to actuate the lever 386 during thehigh vacuum which will in turn engage the lower stop pin 380 andpositively open the choke a small amount. At such times as substantiallyno vacuum exists in the manifold the piston may take the upper positionshown by reason of the urge of spring 3l2 thereby causing the lever 386to engage the upper stop pin 388 and urge the choke closed.

The thermostatic bimetallic element 384 isl preferably secured at itsinner end so as to rotate the crank 382, and at its outer end is adaptedto hook upon a stud 385. Upon heating of the element, due to itsposition adjacent some member of the internal combustion engine such asthe exhaust manifold, tension tending to close the choke valve isgradually released due to the coiling action of the thermostat element,and when the element becomes hot enough, the outer end of the elementmay leave the stud 385 and coil in a clockwise direction until itstrikes the abutment 383, whereupon the thermostat element will commenceto urge the choke valve to an open position. It will be readilyappreciated that for adjustment purposes the stud 385 and stop 383 maybe secured to a revolvable shell 386 which may be frictionally orotherwise secured in any position to adjust the tension on thethermostatic ribbon or element.

As in the modification of Figure 8, the carburetor 298 may have a meansfor positively opening the choke by extreme movement of the` agenten Vthrottle valve,` there: beingr provided for this purpose, a rod 314pivot-,ally secured: in: one end of the double crank 2&8, and slidablyengagingfa swivel 'collar 3.164 on the cra-nk 3|f8 controlling thethrottle. A fixed collar 32ll-on the` end. of the rodi serves to engagethe swivel collar upon` open.- ing the. throttle wide, therebyv allowingthe choke valve to be opened by extrememovement of. the throttle valve.

The further modified form ofrFi'gui-.e 10\isw also illustrated. asaadapted .to aA downdraft` carburetor 33D 'having a choke. valve 332 andthrottle 334,. 'llhe choke valve mayv beof the unbalanced. type and islcarriedkon ae shaft 336 to whichf is also secured a cam 338 and spiral'thermostatic. ele:- ment` 3.411 Api-voted: lever 342 havingpreferably aroller follower 34141` is adapted to engage the outer cam, surface 346,and engage the inner cam surface 348. byv the: spur 3501 oni the lever,vto which is; also. secured.` the outery endof the. thermostatic`element 3.40. By: the.` usel of. a suction motor connectedto theintakemanifoldasfatr35fl., which. motor comprises. an cylinder 352'` andipiston 354, actuation; of' the levery 342: through the connecting link356 takes place in accordance with the manifold; vacuum-except asmodified by' the heat of the resilient thermostatic element, which isexposed to a source of ht resulting either directly or indirectly fromengine operation.

The outer cam surface 346 has a steep nearly radial portion 341 and alowpitched spiral portion 345 which are adapted to engage the rollerfollower 344. The steep portion 341 acts as a choke lock preventing thechoke from opening due to suction on the unbalanced valve, without theaid of the suction motor 352, the mechanical advantage of the steep camsurface when driving the roller being too low to permit choke openingdue to suction alone. The generally spiral section 348 provides a meansfor determining the position of the lever 342 once the choke has opened,and thereafter may regulate the tension on the thermostat since movementof the lever, through the spur 350 varies the position of the outer endof the thermostatic ribbon. Should the choke for any reason stick afterthe engine commences to run, manifold vacuum acting on the piston 354will tend to rock the lever, urging the spur 350 against the inner camsurface 348 thereafter forcing the choke open.

Operation of the device illustrated in Figure produces a change inthermostat adjustment with changes in manifold vacuum. For example,lupon sudden opening of the throttle, a cold motor is often prone to.back fire due to the temporary existence of too lean a mixture, butwith the structure shown, upon sudden drop in manifold vacuum as whenthe throttle is quickly opened, the piston 354 is released, allowing thespring 353 to urge the piston upward and rotate the lever 342counterclockwise thereby instantaneously tightening the thermostatribbon, and Inomentarily increasing the tendency to choke, which as aresult enriches the mixture and tends to compensate for the suddenvariations in throttle opening. It of course will be understood that thelow pitch cam surface 345 regulates at all times the maximum tensionwhich may be applied to the thermostatic ribbon for any given throttleposition, and that the above operation occurs only at such times as whenmanifold vacuum is suiciently high to actually remove the roller fromthe cam contour. This action may be termed an economizer action, for innormal steady operation, the choke. is olered: little resistance toopening. permitting economical operation while upon sudden departurefrom steady operation, the. resistance i is instantly increased:r

Thoughf several: embodiments. of.y the. invention have. beenillustrated` and described, it isito` be understood that: the inventionis not limited thereto but may be embodied in variousfmechanicalzforms.For: example;k various;` elements ofthe modification-szmay` beinterchanged, a's one may .benfound morer..desirable. irr. a specificeasel than another. As many such'. changes in construction and;arrangement of' parts may bei made without departing from the spiritiofthe. invention, as will be` apparent. tothosefs-killed. in the` art,reference will lnefliaditof` theapp'en'de'd claims. for a defnitionlofi` ther limits 1 off the invention;V

Featuresl not claimed herein; are claimed in-my cnpending.-application,Serial. No; 395531, filed September 7-, 1.935,. as' a; divisioni. of mycopending application" Serial; No.. 6.4.1,898gabo-ve referred to;

I claim; y

1.In` a, carbureton. an unbalanced choke valve; resilientthermostati'csm'eansfor urging saidvalve towards closed; positiom and:aamanifoldi vacuum' operatedr piston. having.: ai resilient: operatingconnection with said valve for urging said valve toward open positionagainst the urge of said thermostatic means.

2. In a carburetor, a choke valve, a throttle valve, a manifold vacuumresponsive motor, resilient thermostatic means for urging said chokevalve closed, a resilient connection between said motor and choke valvefor urging said choke valve open upon high vacuum in said motor, andmeans for positively opening said choke valve upon movement of saidthrottle valve to substantially Wide open position.

3. In a carburetor choke, an unbalanced butterfly choke valve,thermostatic means forcibly urging said valve closed when cold, andforcibly urging said valve open when heated, and manifold vacuumsensitive means operatively connected to said valve for positivelyYopening said valve upon existence olf normal operating vacuum in themanifold.

4. In a carburetor, a pressure responsive choke valve, a throttle valve,thermostatic means for closing and opening said choke valve, manifoldvacuum sensitive means including a cylinder and a piston for openingsaid choke valve, and connecting means between said choke valve andthrottle valve to open said choke valve when said throttle valve isopened substantially wide.

5. A control mechanism for an internal combustion engine carburetorhaving a choke valve and a throttle, comprising a thermostat connectedto the choke valve and tensioned when cold to hold the choke valveclosed for starting and to permit the same to fully open when the enginereaches a predetermined temperature, a piston actuated by vacuumposterior to the throttle when the engine is running, and yieldablemeans connecting the piston to the valve in opposition to thethermostat.

6. A control mechanism for an internal combustion engine carburetorhaving a choke valve and a throttle, comprising a shaft, a lever xed onthe shaft, means connecting the lever to the choke valve, a thermostatconnected to the shaft and arranged to rotate the same to close thechoke valve when the engine is cold, an ear on the lever, a rodextending through the ear, a

" spring fixed on the rod and bearing against the ear, and meansconnected to the rod and actuated by vacuum posterior to the throttlefor tensioning said spring to oppose the thermostat and open the chokevalve.

7. A carburetor havinga choke valve, a carbureting passage, athrottlevalve controlling the carbureting passage, temperature responsive meansadapted to urge the choke valve toward the closed position when cold andto permit the choke valve to fully open when heated to a predeterminedtemperature, pressure responsive means communicating with thecarbureting passage posterior to the throttle valve, and yielding meansconnecting the pressure responsive means to the temperature responsivemeans.

8. A carburetor having an air inlet passage, a pressure responsive chokevalve controlling the air inlet passage, a carbureting passage, athrottle valve controlling the carbureting passage, temperatureresponsive means controlling the choke valve, iluid pressure actuatedmeans communicating with the carbureting passage posterior to thethrottle valve to modify the action of the temperature responsive means,and yielding means between the temperature responsive means and the uidpressure actuated means.

9. A control mechanism for a carburetor having an air inlet passage anda carbureting' pas* sage, a pressure responsive choke `valve controllingthe air inlet passage, a throttle valve controlling the carburetingpassage, temperature responsive means `adapted to exert aforce when coldand to discontinue said force when heated to a predeterminedtemperature, connecting means -between the temperature responsive meansand the choke valve, and pressure responsive means yieldingly connectedt0 said connecting means.

10. A control mechanism for-a carburetor having an air inlet passage anda carbureting passage, a pressure responsive choke valve controlling theair inlet passage, athrottle valve controlling the carbureting passage,temperature responsive means adapted to exert a force when cold and todiscontinue said force when heated to a predetermined temperature,connecting means between the temperature responsive means and the chokevalve, and pressure responsive means communicating with the carburetingpassage beyond the throttle valve and yieldingly connected with theconnecting means to modify the action of the temperature responsivemeans.

STUYVESANT C. SMITH.

